Blade sharpening system and method

ABSTRACT

A system for sharpening circular, knife edged blades operates to bias an infeed grinding wheel into contact with the first edge of the blade and an outfeed grinding wheel into contact with the second edge of the blade. The grinding wheels are spaced so that they contact the respective edges of the blade at a point which is spaced by no more than 1 inch from the center line of the blade. Contact between the grinding wheels and the blade is accomplished solely by pushing the wheels from their sides which are opposite the blade contacting surface. The system includes provisions for adjusting the position of the wheels relative to the blade so as to accommodate blade wear.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority of provisional patent application Ser. No. 61/432,926, “Blade Sharpening System and Method”, filed Jan. 14, 2011, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to sharpening systems and, more particularly, to systems for sharpening circular, knife edged blades.

BACKGROUND OF THE INVENTION

Consumer sized rolls of paper products such as paper toweling, bathroom tissue, and the like are frequently prepared by rolling paper stock into relatively wide rolls having a diameter in the range of 4-12 inches. These rolls are referred to as “logs” in the industry, and are subsequently cut into lengths of 4-12 inches to produce a consumer unit of product. In other instances, the stock is folded into elongated bodies having a square cross-section corresponding to folded paper towels. These bodies are also called “logs” and, like the circular cross-section logs, they are subsequently cut into various lengths. In either instance, this cutting is accomplished through the use of large, circular knife edged blades referred to as “log saw blades”. These blades have a diameter typically in excess of 2 feet, and are required to have a very sharp edge so as to effectively cut the logs. The paper product dulls the knife edged blades very quickly; hence, they must be resharpened frequently. It is preferable that the resharpening process not require removal of the blade from the log saw apparatus so as to minimize downtime, and it is most preferable that the sharpening operation may be carried out while the blade is in use.

The prior art has implemented a number of systems which operate to contact a moving, circular, knife edged blade with one or more stationary or moving sharpening stones. Commonly employed prior art systems operate to contact the blade with spring-loaded abrasives which push the blade from one direction and pull it from another; however, this type of system can cause twisting of the knife due to uneven spring pressure. Such twisting can cause scalloping of the blade. Scalloping is a term used to describe the condition of a knife edged blade that has become out of round. This scalloping shortens blade life and reduces the quality of the finished product. Prior art sharpening systems cannot fully control twisting of the blade due to uneven spring pressures, and hence cannot adequately prevent blade scalloping.

Thus, there is a need for a system for sharpening circular, knife edged blades such as log saw blades, which system eliminates problems of blade twisting. It will also be noted that since the blades are sharpened on a very frequent basis (typically at least several times an hour) blade diameter will change rapidly, and hence such systems must be regularly adjusted so as to maintain alignment with the blade. Therefore, it is further desirable that any such blade sharpening system be amenable to rapid and precise readjustment.

As will be explained in detail hereinbelow, the present invention provides a system for sharpening circular, knife edged blades such as log saw blades which eliminates or greatly minimizes blade scalloping. The system of the present invention may be utilized on a blade while it is in service, and the system is configured so as to allow for safe and accurate front surface manual adjustment and/or automatic adjustment, thereby minimizing the chance of injury to a user while maximizing the operational time of the cutting system.

BRIEF DESCRIPTION OF THE INVENTION

Disclosed is a system for sharpening a circular, knife edged saw blade. The system includes a grinding head assembly having a first, infeed, grinding wheel and a second, outfeed, grinding wheel. The grinding head assembly operates to bias the infeed grinding wheel into contact with the first edge of the blade and to bias the outfeed grinding wheel into contact with the second edge of the blade such that each of the grinding wheels contacts its respective edge of said blade at a point which is spaced by no more than 1 inch from the center line of the blade. In particular instances, the grinding wheels contact their respective edges of the blade at a point which is no more than ½ inch from the center line of the blade. In specific instances, the grinding head assembly is further operable to bias the grinding wheels into contact with the blade so that a line tangent to either of the grinding wheels and parallel to the center line of the blade is spaced from that center line by a distance of no more than ¼ inch and in some instances no more than ⅛ inch.

In specific instances, grinding wheels are retained within cartridges which may be coupled to the remainder of the system by a quick-release fitting such as a fitting utilizing a dovetail joint.

In particular instances, the system operates to bias the first and second grinding wheels into contact with the circular knife edged blade solely by pushing each of the wheels into contact with the blade from the side of the grinding wheel opposite the surface thereof which contacts the blade. In certain embodiments, the system operates to bias the grinding wheels by means of a force applying system, such as a pneumatic system, which does not include any spring elements.

In specific instances, the grinding head assembly may include a control for adjusting the position of the grinding wheels relative to the blade. This may be a manual control mounted on the front face of the grinding head, or it may be an automatic control. Further disclosed are methods for the use of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an embodiment of the system of the present invention;

FIG. 2 is a side view of the embodiment of FIG. 1;

FIG. 3 is an enlarged view of a portion of the system of FIG. 1;

FIG. 4 is an enlarged view of a portion of the system of FIG. 2; and

FIG. 5 is an enlarged detail of FIG. 3 better showing the positioning of the grinding wheels with regard to the knife edged blade.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a system for sharpening a circular, knife edged blade such as a log saw blade. The system of the present invention operates to support a first and a second grinding wheel, typically in a cartridge, in a precise relationship with the blade such that the grinding wheels are positioned on opposite sides of the blade so as to be engageable with a respective knife edged cutting surface of the blade. It is significant that in the present invention, the grinding wheels are supported in a specific geometric relationship at, or very near to, the center line of the blade, and it is further significant that the system of the present invention operates to push both of the grinding wheels into firm contact with the blade by applying a pushing force directed to the sides of the grinding wheels which are opposite the portion of the grinding wheel which contacts the log blade. This push-push type of contact, together with the center line based alignment of the grinding wheels, has been found to eliminate or greatly minimize scalloping of the blade during the sharpening process.

Also this system is a “free floating” system which, in particular instances, uses a controlled air, or other gas, pressure to hold the grinding wheels in a constant level of contact with the blade during sharpening, with the result that even if the blade wobbles laterally, contact is maintained with the bevel of the cutting edge. This is in contrast to the operation of prior art systems which use a push-pull arrangement of grinding wheels in which a spring configuration functions to hold the grinding wheels against the blade. In these types of spring-based systems the spring pressure changes constantly as the springs vibrate in use, or are stressed, compressed, or fatigued from long-term usage. As a result, the prior art systems allow for undesirable blade motion during the sharpening process, which can result in blade scalloping.

In contrast to prior art systems, the positive, push-push clamping effect of the system of the present invention prevents blade wobble and scalloping. The fact that the system of the present invention may be implemented so as to eliminate the use of springs in supplying the force for urging the grinding wheels into contact with the blade further prevents blade wobbling and scalloping.

The present invention may be implemented in a number of different configurations dependent upon particular log saw tooling in which it is installed. All of such embodiments are within the scope of the present invention, and for purposes of illustration one specific type of installation will be discussed.

Referring now to FIG. 1, there is shown a front view of one embodiment of a sharpening system (10) structured in accord with the principles of the present invention. The system (10) is positioned and configured so as to sharpen a knife edged log saw blade (12). Not shown is a blade drive assembly for rotating the blade (12); however, such assemblies are common and the particular configuration of the assembly will depend upon the specific implementation of the system. FIG. 2 shows the system (10) of FIG. 1 in a side view.

FIGS. 3 and 4 show corresponding enlarged portions of the illustrations of FIGS. 1 and 2 and better depict the components of the present invention. FIG. 3 shows the system (10), in a front view, as positioned to sharpen a circular knife edged blade (12) which, in the use of the system, will be rotating in the direction shown by arrow A, and operational to cut roll, or square-stacked, logs of paper stock. The system of FIG. 3 includes a grinding head assembly (14) which is operable to support a first grinding wheel (16) which is referred to as an “outfeed” wheel, since it is located so as to contact what is known in the art as the outfeed cutting portion of the blade, which in the cutting process is the trailing portion. The system further includes a second grinding wheel (18) known as an “infeed” wheel and which contacts the infeed portion of the blade (that is to say the portion of the blade that first encounters the log). In this regard, each of the grinding wheels (16) and (18) is supported, in this embodiment, by a respective grinding wheel cartridge (20) and (22) which facilitates the ready removal and replacement of the grinding wheels; although, in other embodiments the grinding wheel cartridges may be otherwise supported. A typical knife edged circular blade has a 12 degree included angle bevel on its cutting edge, and the grinding wheels (16) and (18) are angularly positioned to contact the blade at an appropriate angle, which is generally 15 degrees.

Cartridge or cassette systems which may be adapted for supporting the grinding wheels are shown, in another context, in U.S. Pat. Nos. 6,732,625; 5,058,475; and 5,083,489, the disclosures of which are incorporated herein by reference. Other cartridge or cassette arrangements may be likewise utilized, and in some instances, the grinding wheels may be directly affixed to the grinding head assembly (14).

In particular instances, the system may include grinding wheel cartridges which are coupled to the grinding head assembly by quick-release couplers, thereby facilitating their replacement. For example, the cartridges may joined to the remainder of the apparatus by a dovetail joint operable in combination with retainers such as screws, cams or the like, which will enable the cartridge to be accurately placed and locked in a proper alignment with the remainder of the apparatus.

FIG. 4 is a corresponding side view of the portion of the system illustrated in FIG. 3 and illustrates the grinding wheels (16) and (18) as supported by their respective cartridges (20) and (22) in engagement with the saw blade (12). As will be seen, the grinding head assembly biases the outfeed grinding wheel (16) into contact with the outfeed edge of the blade (12) and an infeed grinding wheel (18) into contact with the infeed edge of the blade (12). It is notable that in this system the biasing force is applied to the wheels from a direction indicated by arrows B and C, which direction is from a side of the wheel opposite the side thereof which contacts the blade. This push-push force arrangement provides a positive clamping action which captures the blade and prevents lateral wobble and oscillation thereby minimizing scalloping.

Referring now to FIG. 5, which is an enlargement of a portion of FIG. 3, there will be seen a further feature of the present invention. As shown therein, the grinding wheels (16) and (18) are placed very close to the center line of the log blade (12). This placement further enhances the stability of the blade during the sharpening process. As specifically shown in FIG. 5, the contact point between the outfeed grinding wheel (16) and the blade (12), and the contact point between the infeed grinding wheel (18) and the blade (12) are spaced apart from one another by a distance (D1) which is no more than 2 inches, and in this particular embodiment, a distance of 0.9494 inch. Taken with regard to the center line of the blade, the contact point of each of the grinding wheels is spaced therefrom by one half the above-stated distances, and is no more than 1 inch.

Furthermore, in the illustration of FIG. 5 it will be seen that the grinding wheels (16, 18) are spaced laterally from one another by a very small distance (D2), which is generally no more than ½ inch. In the specific embodiment of FIG. 5, the grinding wheels (16, 18) are spaced from one another by a distance (D2) which is less than ¼ inch, namely a distance of 0.2442 inch. Thus, each of the grinding wheels (16) and (18) will be positioned so that a line tangent to the wheel and parallel to the center line will be spaced from that center line by no more than ¼ inch, and in this particular instance less than ⅛ inch.

In the operation of a typical log saw apparatus, sharpening occurs very frequently, owing to the highly abrasive nature of the paper stock which is being cut. This frequent sharpening will reduce the dimensions of the circular knife edged blade and require frequent adjustments of the position of the sharpening system during the cutting process. As shown in the figures, the system includes controls (30) for adjusting the position of the grinding wheels (16) and (18) relative to the blade, and it is a notable feature of the present invention that these adjustment controls are placed on a front surface of the grinding head assembly (14) at a location spaced apart from the cutting edge of the blade (12). This positioning avoids the need for an operator of the system to reach across the cutting edge of the blade when making such adjustments as in prior systems, and thereby enhances the safety of the system. The fact that the present invention utilizes a push-push mode of operation facilitates the positioning of the controls on the front face of the assembly since it does not require two-sided access to any components as would be the case in push-pull prior art systems.

While the embodiment of the invention shown in FIGS. 1-5 includes manual controls (30) for adjusting the position of the grinding wheels (16, 18), this adjustment may also be implemented automatically through the use of mechanical and/or electronic sensors and actuators. For example, the adjustment system may operate to sense when a sharpening cycle has been implemented and/or its duration, and thereby determine if the position of the grinding wheels needs to be adjusted relative to the blade. This type of system may be implemented through the use of a mechanical linkage such as a ratchet assembly. Such a system may incrementally vary the grinding wheel position after each sharpening cycle or after a predetermined number of cycles. In other embodiments, the system may be operable to sense changes in the diameter of the blade and to adjust the grinding wheels accordingly. Such automated adjustment systems may be utilized in conjunction with a manual adjustment system, or as a substitute therefor.

The embodiment of the sharpening system described with regard to FIGS. 1-5 uses a pneumatic system in which air powered pistons push the grinding wheels into contact with the blade. As detailed above, use of a pneumatic system eliminates the need to employ springs or like mechanical elements for transmitting a biasing force for urging the grinding wheels into contact with the blade, thereby minimizing blade wobble and scalloping. There are a number of such pneumatic systems available for this purpose. While the foregoing describes the use of a pneumatic system to bias the grinding wheels into contact with the blade in a push-push mode, such function may be achieved through the use of other types of actuators, including hydraulic actuators, electromagnetic actuators, and the like.

The present invention may be implemented in still other embodiments and configurations, and such will be apparent to those of skill in the art in view of the teaching presented herein. While this system has primarily been described with reference to the sharpening of circular blades used for cutting logs of paper products, it is to be understood that it can be used to sharpen any type of circular, knife edged blade. The foregoing drawings, discussion, and description are illustrative of specific embodiments of the invention but are not meant to be limitations upon the practice thereof. It is the following claims, including all equivalents, which define the scope of the invention. 

1. A system for sharpening a circular knife edged blade, said system comprising: a grinding head assembly, said grinding head assembly including a first, infeed, grinding wheel, and second, outfeed, grinding wheel, said grinding head assembly being operable to bias said infeed grinding wheel into contact with a first edge of said blade and to bias said outfeed grinding wheel into contact with a second edge of said blade such that each of said grinding wheels contacts its respective edge of said blade at a point which is spaced by no more than 1 inch from the center line of said blade.
 2. The system of claim 1, wherein said grinding head assembly is configured so that said grinding wheels contact their respective edge of said blade at a point which is no more than ½ inch from the center line of said blade.
 3. The system of claim 1, wherein said grinding head assembly is further operable to bias said grinding wheels into contact with the blade such that a line tangent to either of the grinding wheels and parallel to the center line of said blade is spaced from said center line by a distance of no more than ¼ inch.
 4. The system of claim 3, wherein said line tangent to either of said grinding wheels is spaced from the center line of said blade by a distance of no more than ⅛ inch.
 5. The system of claim 1, wherein said grinding wheels are each retained within a respective cartridge and wherein said grinding head assembly is operable to bias said cartridge and said retained grinding wheels into contact with said blade.
 6. The system of claim 5, wherein each of said cartridges is retained in said grinding head by a dovetail joint.
 7. The system of claim 1, wherein said grinding head assembly is operable to bias said first and second grinding wheels into contact with said blade solely by pushing each of said wheels into contact with said blade from a side of said grinding wheel opposite the surface thereof which contacts said blade.
 8. The system of claim 1, wherein said grinding head assembly further includes at least one control for adjusting the position of said grinding wheels relative to said blade.
 9. The system of claim 8, wherein said at least one control is a manually activatable control located on a front face of said grinding head assembly which face is displaced from said blade so that said control may be manually adjusted without requiring a user to reach across the blade.
 10. The system of claim 8, wherein said at least one control is an automatic control.
 11. The system of claim 10, wherein said at least one control operates to sense the implementation of a sharpening cycle by said system and to adjust the position of said grinding wheels in response thereto.
 12. The system of claim 10, wherein said at least one control operates to sense the diameter of said blade and to adjust the position of said grinding wheels in response thereto.
 13. The system of claim 1, further including a pneumatic system which is operable to bias said infeed grinding wheel into contact with a first edge of said blade and to bias said outfeed grinding wheel into contact with a second edge of said blade.
 14. A method for sharpening a circular knife edged blade, said method comprising the use of the sharpening system of claim
 1. 15. A system for sharpening a circular knife edged blade, said system comprising: a grinding head assembly, said grinding head assembly including a first, infeed, grinding wheel, and second, outfeed, grinding wheel, said grinding head assembly being operable to bias said infeed grinding wheel into contact with a first edge of said blade and to bias said outfeed grinding wheel into contact with a second edge of said blade solely by pushing each of said wheels into contact with said blade from a side of said grinding wheel opposite the surface thereof which contacts said blade.
 16. The system of claim 15, wherein the system does not employ any spring linkage to push said grinding wheels into contact with said blade. 